1. Technical Field
The present invention relates to a method for producing acoustic emissions and a device for such production.
Also a computer program and a computer program product for these purposes is disclosed.
2. Prior Art
The engine of e.g. a vehicle, e.g. of a combustion engine of the vehicle, and primarily, a heavy vehicle, such as a truck or a bus, is a source of severe acoustic emissions, particularly noise, which includes external noise as well as internal noise inside the vehicle compartment. Considerable efforts and research are performed to decrease acoustic emissions from such engines.
Such efforts and research include inter alia the intensity and level of the sound, its frequency distribution, source analysis etc. Such efforts and research include both investigations regarding actual sound characteristics and the results of attempts to amend the sound characteristics, e.g. decreasing the sound emission, changing the frequency distribution, etc.
Further, an extremely complex phenomenon is determining how acoustic emissions from e.g. the engine is transmitted in and throughout the vehicle and, thus, is emitted from the vehicle. Normally, a complex empiric approach is used.
Still further, attempts are being performed to find theoretical models for calculating acoustic transmission in and from a vehicle structure.
Thus, according to what was previously known, the emission profile of an engine is detected by, primarily, a microphone configuration by means of which the acoustic emission in different directions etc may be detected. Amendments with respect to the acoustic emission profile is performed by means of so-called lead wrapping, which comprises wrapping various parts of the engine using comparatively thin lead plate portions in order to isolate desired portions in order to investigate how various portions of the engine affect the acoustic emission profile. Lead is easy to shape around desired portions of the engine and has excellent attenuation properties. However, such a covering technique is extremely time consuming so this technique is far from perfect, apart from the fact that lead has toxic properties.
This previously known technique is quite an ineffective tool when it comes to detailed investigations regarding acoustic emission generation, acoustic transmission in a vehicle body, generating basis for calculation models etc, and does not provide the necessary information.
An object of the present invention is, primarily, to provide a new and improved technique for generating engine acoustic emissions, obtaining information regarding acoustic transmission in a vehicle body, determining the influence of acoustic parameter values and variations, providing a basis for calculation models etc,